Dell 2007WFP help

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  • lnsulans
    Member
    • Apr 2016
    • 13
    • Canada

    #1

    Dell 2007WFP help

    Hi,

    I have a broken Dell 2007WFP. It powers on, then starts to show the dell startup logo, then shuts off. It does this repeatedly, and the time it spends on/off seems to vary quite a bit. It does this both with and without a computer plugged into it (and when it is connected to a computer, it leads to a continual cycle of monitor connected/disconnected alerts).

    It is shutting off fully (power light off) not going to standby (power light orange).

    I've attached photos of the circuit boards to this post.

    First two are the inverter, then the power supply, then video board, then USB board.

    I've read through most of the other 2007WFP threads here than I can find, but I'm not entirely sure where to go from here.

    Stuff I have tried (as suggested in some other threads):
    • Checked the fuses - all seem to be ok (I may have missed some, but I think I checked all of them)
    • Checked resistance of the transformers (see: https://www.badcaps.net/forum/showpo...6&postcount=14) - the resistances are all very close, few ohms difference at most <1% variance
    • Checked that the CCFL bulbs work - I took the monitor most of the way apart, used a working monitor's power supply to power the bulbs, and they lit up solid and bright and stayed that way for a few minutes until I turned it off
    • Tried powering the CCFLs from that working power supply with the monitor assembled and plugged into a computer - screen just stayed black, power light cycled green and off every few seconds (I didn't expect this to work, but I figured it was worth trying)



    Based on some reading elsewhere on this forum, I tried to confirm if the 5V and 3.3V supplies were working properly. I didn't get anywhere with that.

    There is 19V being supplied to the inverter, both when the monitor is on and off through its power cycling.

    I also took some measurements at the pins which connect the USB board to the video board, I'm not sure if these are at all useful. The following measurements correspond to looking at those pins from the bottom of the video board (top left to bottom right):

    0.03 0
    3.3 3.3
    0 0
    3.3 5.1
    11.9 11.9
    19 19


    Notably, when the monitor flipped off, these measurements went to:

    1.24 0
    1.48 1.65
    0 0
    0 0
    0 0
    19 19



    Any suggestions on where to go from here are appreciated. I'd like to narrow down the problem a bit if possible before I just go replace a ton of parts. I'd rather not need to make three different digikey orders as I sort through this.
    Attached Files
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Dell 2007WFP help

    This is just a always on 19VDC single power supply.
    So are you saying that when the monitor is plugged in but the power switch is not activated the 19VDC to the inverter is going up and down or it is steady?

    This board: https://www.badcaps.net/forum/attach...8&d=1461731707
    It takes the 19V input and down converted to various low Voltages to run other boards and circuits.
    You may want to read this thread regarding to bad resistor under the white glue on that down converter board.
    https://www.badcaps.net/forum/showth...ight=DELL+2007
    Last edited by budm; 04-26-2016, 11:14 PM.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment

    • lnsulans
      Member
      • Apr 2016
      • 13
      • Canada

      #3
      Re: Dell 2007WFP help

      Originally posted by budm
      This is just a always on 19VDC single power supply.
      So are you saying that when the monitor is plugged in but the power switch is not activated the 19VDC to the inverter is going up and down or it is steady?
      Measured again. 19VDC to invertor board is steady, both when the power LED is green and off.

      This board: https://www.badcaps.net/forum/attach...8&d=1461731707
      It takes the 19V input and down converted to various low Voltages to run other boards and circuits.
      You may want to read this thread regarding to bad resistor under the white glue on that down converter board.
      https://www.badcaps.net/forum/showth...ight=DELL+2007
      I peeled off that white glue and tried to measure the resistors, but I can't seem to get the pads clean enough to get a good contact with the meter. Any suggestions on getting rid of all of it?

      Should I just desolder them and test them off board? I have a hot air rework blower, its not really a problem for me to do that.

      Comment

      • stj
        Great Sage 齊天大聖
        • Dec 2009
        • 30931
        • Albion

        #4
        Re: Dell 2007WFP help

        use a file or stone to sharpen your meter probes.

        Comment

        • lnsulans
          Member
          • Apr 2016
          • 13
          • Canada

          #5
          Re: Dell 2007WFP help

          All of those resistors except the 2.7k read the right values. The 2.7k reads open.

          New problem though: I managed to screw up desoldering the 2.7k. The 2.7k came off fine, the resistor one above it I managed to accidentally shift, and one of the pads came off with it (I still have that resistor).

          Any idea where that missing pad connects to? If it connects to the cap beside it, that's really easy to bridge.

          If I did kill the board, I'm not too disappointed. I was expecting to need to buy a new monitor anyways, but it would be nice to get it to work.

          I know its not the best photo, I'll try to get something better later today, but I don't really have anything good for photographing stuff that small.
          Attached Files

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #6
            Re: Dell 2007WFP help

            If you clean off those flux or what ever in that section then we can see the traces better.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment

            • lnsulans
              Member
              • Apr 2016
              • 13
              • Canada

              #7
              Re: Dell 2007WFP help

              I fixed it. I bridged that cap with a blob of solder to the resistor marked 473 (the one up and to the right of the cap in the photo I posted in my last post), and replaced the burnt out 2.7k with a new one. It works now.

              Thanks.

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #8
                Re: Dell 2007WFP help

                Thanks for the follow-up.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment

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